DESCRIPTION (Applicant's Description): This application focuses on elucidating the normal functions of a recently cloned human gene, retinitis pigmentosa 1 (RP1), and the mechanisms by which the mutant forms of the RP1 gene cause retinal degeneration. Retinitis pigmentosa (RP) is the most common form of inherited retinopathy, affecting 1 in 3.500 people world wide (1.5 million). RP is characterized by night blindness and progressive degeneration of the peripheral retina, culminating in severe reduction of visual fields and in blindness. We have recently identified a novel retinal photoreceptor- specific gene on chromosome arm 8q in which nine mutations were found to cause the RP1 form of autosomal dominant RP in seventeen unrelated families. It is unclear whether mutations in RP1 represent loss-of-function or dominant-negative alleles of the RP1 gene. The protein encoded by this gene consists of 2,156 amino acids; its function is unknown although its amino terminus has significant homology to that of human doublecortin, and its carboxy terminus contains a nucleoside diphosphate kinase domain and several nuclear localization signal domains. We mapped the mouse homolog of the human RP1 gene to mouse chromosome 1 where there is no existing mouse retinal degenerative mutant. In this application we plan: (1) to generate and characterize transgenic mice that over-express wild-type or mutant Rp1 genes in a pattern that recapitulates the pattern of endogenous Rp1 expression; (2) to generate and characterize mice without the Rp1 gene; and (3) to determine the sub-cellular localization of wild-type and mutant Rp1 proteins. These studies will lead to a better understanding of the normal function of the RP1 gene during retinal development. The characterization of molecular pathways in mouse models of RP1 will facilitate the prevention and treatment of retinal degenerative diseases in humans. Although there have been dramatic successes in recent years in the identification of multiple genes that can cause retinal diseases, very little is known about how mutations in these genes cause diseases. A number of these disease genes display complex patterns of gene expression; some mutations that cause dominant retinal diseases are likely to be gain-of-function mutations. Thus, a combination of the transgenic technology using bacterial artificial chromosome and the knockout technology can be widely applicable for making mouse models of these retinal diseases, and our studies of RP1 will provide an example for studying functions of these genes in vivo.